A mechanical seal, an example of a sliding component, is evaluated in its performance by a leakage rate, a wear rate, and torque. In conventional techniques, by optimizing the sliding materials and the sliding face roughness of mechanical seals, their performance is increased to achieve low leakage, long life, and low torque. However, due to growing awareness of environmental problems in recent years, a further improvement in the performance of mechanical seals has been demanded, and technology development beyond the limits of the conventional techniques has been required.
Under such circumstances, as one used in an oil seal device for a rotating component such as a turbocharger, for example, a known one includes a rotating shaft rotatably placed in a housing, a disk-shaped rotor rotating with the rotating shaft, and a disk-shaped stator that is fixed to the housing and abuts on an end face of the rotor to prevent leakage of oil from the outer peripheral side to the inner peripheral side, the stator having an abutment face provided with an annular groove for generating positive pressure by the centrifugal force of fluid, to prevent leakage of oil from the outer peripheral side to the inner peripheral side (see Patent Document 1, for example).
Another known one in a rotating shaft seal device for sealing toxic fluid, for example, includes a rotating ring with a rotating shaft and a stationary ring mounted to a casing, one of the rotating ring and the stationary ring having a sliding face provided with spiral grooves with an end on the high-pressure side being in a dead-end shape, for drawing in liquid on the low-pressure side toward the high-pressure side by rotation of the rotating ring, to prevent leakage of sealed fluid on the high-pressure side to the low-pressure side (see Patent Document 2, for example).
Another known one as a face seal structure suitable for sealing a drive shaft of a turbocharger against a compressor housing, for example, has a pair of seal rings working together, one being provided as a rotating component and the other being provided as a stationary component, the seal rings each having a sliding face formed substantially radially, and forming, between the sliding faces, a seal gap for sealing an area provided outward of the sliding faces against an area provided inward of the sliding faces during operation, at least one of the sliding faces being provided with a plurality of circumferentially spaced recessed portions effective for feeding gas, the recessed portions extending from one peripheral edge of the sliding face toward the other peripheral edge, the recessed portions having an inner end radially spaced from the other peripheral edge of the sliding face, to seal a non-gas component in a gas medium containing the non-gas component (see Patent Document 3, for example).